Once a hose has been fully compressed by a hose clamp, further application of force to the screw of a worm drive hose clamp does nothing to improve the seal at the joint. Moreover, continued application of force, after full compression of the hose, will be destructive rather than productive.
In worm drive clamps, once the strap has stalled, continued rotation of the screw will move the screw along the strap into and through the housing. If the housing has been designed to resist this movement of the screw, the continuing rotation must be accommodated by housing flexure until one or more of the restraining member fails.
When the strap can no longer move due to full compression of the hose, it will attempt to accommodate the continuing effort by elimination of the angular thrust vector of the worm. It does this by aligning itself, or attempting to align itself to neutralize the thrust of the screw. This movement forces the screw thread to engage the strap at the serration edge. Continuing rotation accelerates the movement of the strap from under the screw.
One destructive force that is brought into play whenever loading is applied beyond that required to fully compress the hose is thrust of the strap which may force the legs of the housing to deflect and open, spreading the retaining tabs and fracturing the strap at the aperture therein. Stated in another manner, failure of clamps heretofore known and used is often due to rupture of the strap adjacent aperture therein that accepts the clamp housing due to spreading of the tabs of the housing. Such conventional clamp housings exhibit a pair of coacting lever arms which act to multiply the effect of excessive load applied to the strap by the screw. Therefore, it is apparent that to the extent such lever arms can be reduced and energy can be absorbed in the clamp housing, failure of the clamp strap can be ameliorated.